US20210318372A1

US20210318372A1 - Apparatus for Measuring Insulation Resistance

Info

Publication number: US20210318372A1
Application number: US17/226,470
Authority: US
Inventors: Woo Jung Kim
Original assignee: SK Innovation Co Ltd
Current assignee: SK On Co Ltd
Priority date: 2020-04-13
Filing date: 2021-04-09
Publication date: 2021-10-14
Anticipated expiration: 2041-04-09
Also published as: CN113533853A; US11656265B2; KR20210126860A; US20230243884A1; EP3901640A1

Abstract

The present invention relates to an apparatus capable of measuring an insulation resistance of a battery, and according to the apparatus capable of measuring the insulation resistance of the present invention. A voltage measurement unit may measure a voltage with respect to a potential of a negative terminal of a battery rather than the ground, and thus parameters requiring a high precision may be measured using one device, thereby reducing cost, and, because a first sensing substrate and a second sensing substrate are separated, different potentials may be used as the ground, thereby securing a better insulation performance between the first sensing substrate that is an HV side and the second sensing substrate that is an LV side.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No. 10-2020-0044425 filed Apr. 13, 2020, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an apparatus capable of measuring an insulation resistance of a battery.

Description of Related Art

Recently, an electric vehicle (EV) using an electric battery capable of charging and discharging as a power source has been commercialized as an eco-friendly vehicle. The electric vehicle includes a battery pack used as a power source that provides a high voltage (HV) to a driving electric motor, an inverter, a converter, and the like that require the high voltage for the operation of vehicle, and a lead acid battery used as a power source providing a low voltage (LV) to electronics of vehicle.
At this time, the insulation resistance of the battery pack may decrease or the insulation thereof may be destroyed due to a deterioration. In this case, it is very dangerous because a person touching a chassis may be electrocuted by the high voltage of the battery pack, and thus it needs to continuously measure and monitor the insulation resistance of the battery pack so that the insulation resistance is not reduced less than a certain level.
Meanwhile, an insulation resistance measurement circuit of the related art has been measured with respect to a low voltage (LV) side ground (for example, a negative terminal of a lead acid battery, a chassis).

Claims

1. An apparatus for measuring an insulation resistance of a battery, the apparatus comprising:

a resistance unit including a voltage measurement resistor configured to divide and measure a voltage of the battery; a switching unit coupled to the resistance unit and including a first switch and a second switch for forming a different electrical path; and

a control unit measuring a voltage applied to the voltage measurement resistor and monitoring the insulation resistance of the battery;

wherein the control unit measures the voltage applied to the voltage measurement resistor based on a potential of a negative terminal of the battery.

2. The apparatus of claim 1,

wherein the control unit further comprises a voltage measurement unit configured to measure the voltage applied to the voltage measurement resistor,

wherein the voltage measurement resistor is coupled to the negative terminal of the battery, and

wherein the voltage measurement unit is coupled to the voltage measurement resistor and the negative terminal of the battery.

3. The apparatus of claim 1, further comprising:

a first sensing substrate coupled to the battery; and

a second sensing substrate coupled to a lead-acid battery having a lower voltage than the battery, and isolated from the first sensing substrate,

wherein the resistance unit and the switching unit are mounted on the first sensing substrate, and the control unit is mounted on the second sensing substrate.

4. The apparatus of claim 2, further comprising:

a first sensing substrate coupled to the battery; and

wherein the resistance unit, the switching unit, the voltage measurement unit and the control unit are mounted on the first sensing substrate.

5. The apparatus of claim 1,

wherein the resistance unit further includes a first resistor coupled to a positive terminal of the battery, and a second resistor coupled between the first resistor and the voltage measurement resistor, and

wherein the first switch is coupled between the first resistor and a ground, and the second switch is coupled between the second resistor and the ground.

6. The apparatus of claim 5, wherein the control unit receives the voltage applied to the voltage measurement resistor while operating the first switch in an off state and the second switch in an on state, and receives the voltage applied to the voltage measurement resistor while operating both the first switch and the second switch in the on state.

7. The apparatus of claim 6,

wherein the control unit calculates a positive insulation resistance and a negative insulation resistance by combining Equation 1 and Equation 2 below:

\begin{matrix} V_{Rmes_SW 2} = Pack V \times \frac{R_{L e a k -}  (R_{m e s} + R_{2})}{R_{L e a k +} + R_{L e a k -}  (R_{m e s} + R_{2})} \times \frac{R_{m e s}}{(R_{m e s} + R_{2})} & [Equation 1] \\ V_{Rmes_SW 1_SW 2} = Pack V \times \frac{R_{L e a k -}  (R_{m e s} + R_{2})}{(R_{1}  R_{L e a k +}) + R_{L e a k -}  (R_{m e s} + R_{2})} \times \frac{R_{m e s}}{(R_{m e s} + R_{2})} & [Equation 2] \end{matrix}

where V_{Rmes_SW2}denotes a voltage applied to the voltage measurement resistor when the first switch operates in the off state and the second switch operates in the on state, V_{Rmes_SW1_SW2}denotes a voltage applied to the voltage measurement resistor when both the first switch and the second switch operate in the on state, Pack V denotes a voltage of the battery, R_mesdenotes a value of the voltage measurement resistor, R₁denotes a value of the first resistor, R₂denotes a value of the second resistor, R_Leak+denotes a value of the positive insulation resistance, and R_Leak−denotes a value of the negative insulation resistance.

8. The apparatus of claim 5, wherein the resistance unit further includes a third resistor coupled between the switching unit and the ground.

9. The apparatus of claim 8, wherein the control unit receives the voltage applied to the voltage measurement resistor while operating the first switch in an off state and the second switch in an on state, and receives the voltage applied to the voltage measurement resistor while operating both the first switch and the second switch in the on state.

10. The apparatus of claim 9, wherein the control unit calculates a positive insulation resistance and a negative insulation resistance by combining Equation 3 and Equation 4 below:

\begin{matrix} V_{Rmes_SW 2} = Pack V \times \frac{R_{L e a k -}  (R_{m e s} + R_{2} + R_{3})}{R_{L e a k +} + R_{L e a k -}  (R_{m e s} + R_{2} + R_{3})} \times \frac{R_{m e s}}{(R_{m e s} + R_{2} + R_{3})} & [Equation 3] \\ V_{Rmes_SW 1_SW 2} = Pack V \times \frac{1}{R_{c}} - \frac{(R_{a}  (R_{L e a k -})}{(R_{b}  R_{L e a k +}) + (R_{a}  R_{L e a k -})} \times \frac{1}{R_{a}} \times R_{m e s} & [Equation 4] \end{matrix}

where Equation 4 satisfies

R_{a} = \frac{(R_{1} \times R_{3}) + (R_{1} \times (R_{2} + R_{m e s})) + (R_{3} \times (R_{2} + R_{m e s}))}{R_{1}} R_{b} = \frac{(R_{1} \times R_{3}) + (R_{1} \times (R_{2} + R_{m e s})) + (R_{3} \times (R_{2} + R_{m e s}))}{(R_{2} + R_{m e s})} R_{c} = \frac{(R_{1} \times R_{3}) + (R_{1} \times (R_{2} + R_{m e s})) + (R_{3} \times (R_{2} + R_{m e s}))}{R_{3}}

where V_{Rmes_SW2}denotes a voltage applied to the voltage measurement resistor when the first switch operates in the off state and the second switch operates in the on state, V_{Rmes_SW1_SW2}denotes a voltage applied to the voltage measurement resistor when both the first switch and the second switch operate in the on state, Pack V denotes a voltage of the battery, R_mesdenotes a value of the voltage measurement resistor, R₁denotes a value of the first resistor, R₂denotes a value of the second resistor, R₃is a value of a third resistor, R_Leak+denotes a value of the positive insulation resistance, and R_Leak−denotes a value of the negative insulation resistance.